1. Field of the Invention
The present invention relates to a hemostasis valve, and more particularly, to a hemostasis valve incorporated within an introducer assembly for enlarging and maintaining a percutaneous opening in a given arterial or venous vessel for the purpose of providing a pathway for the introduction of interventional devices.
2. Description of the Prior Art
The introduction of interventional devices into a given arterial or venous vessel for a variety of purposes, such as coronary angiography or for performing percutaneous transluminal coronary angioplasty (PTCA), as well as angiographic procedures, for example, where X-ray contrast fluid is inserted into the coronary artery, has been known for many years. Several techniques for introducing such catheters are available, including the cut-down method and the Seldinger technique. The Seldinger technique involves surgically opening a vein or artery with a needle, inserting a guide wire into the vein or artery through the lumen of the needle, withdrawing the needle, inserting over the guide wire a dilator located inside an associated hemostasis valve and sheath removing the dilator and inserting a catheter through the hemostasis valve and sheath into the blood vessel. In this process, care must be exercised to prevent introduction of air into the vessel and it is desirable to avoid leakage of blood out of the proximal end of the sheath. To avoid the risk of both "air embolism" and "blood contamination of the physician" modern introducers for the placement of such interventional devices as open and closed-end catheters, temporary pacing electrode catheters, guiding catheters, and angioplasty catheters, employ various types of hemostasis valves. Such hemostasis valves must be designed for use with more than one diameter catheter and guide wire that can be introduced within and through the hemostasis valve and outer sheath for the purposes listed above. Guide wires are of extremely small diameters--often less than 0.050 inch. However, many catheters are relatively larger in diameter. Therefore, the prior art has addressed many configurations of hemostasis valves attempting to provide an adequate seal at low and relatively higher blood pressure conditions for both air and blood while accommodating the wide range of diameters of devices inserted through the outer sheath.
Prior art hemostasis valves have, in many instances, been of the gasket sealing type, such as those shown in U.S. Pat. Nos. 4,000,739, 4,424,833, and 4,909,798, which comprise a pin hole and a Y-shaped slit, back-to-back gasket assembly in either one or two-piece parts. The first, doughnut-shaped, gasket is provided with a hole slightly smaller than the diameter of the catheter to be inserted, while the second gasket is provided with a Y-shaped slit. When guide wires or catheters which are too small in diameter are inserted into this hemostasis valve, the sealing advantages of the first doughnut-shaped gasket are no longer available because the larger diameter doughnut holes will not seal around the smaller diameter guide wire or catheter. The two gaskets may be provided as separate back-to-back piece parts or as a single piece part, but in either case, are intended to reduce the possibility that blood would escape the hemostasis valve as the tip of the introduced instrument is withdrawn. Thus, the redundancy of the two seals is expected to reduce such leakage.
In attempts to improve on the back-to-back hole and Y-shaped slit seals, it has been proposed in U.S. Pat. Nos. 4,610,665, 4,610,674, 4,626,245, and 4,673,393 to provide hemostasis valves in either single or multiple combinations where the disk-like valve is provided with a first slit open only to one of the end faces thereof and the second slit open only to the other of the end faces thereof, intersecting at roughly the center of the disk so that a pin hole is effected through the end faces at the intersecting point of the two slits. The end faces of the disk-shaped valve are flat and parallel to one another.
In a further variation on the Y-shaped slit of the '739 patent, for example, and the criss-crossing partial slits of the '665 patent, for example, it has also been proposed in U.S. Pat. Nos. 4,798,594 and 4,895,565 to provide a Y-shaped slit through the disk-shaped hemostasis valve body by pressing a die through the body while simultaneously rotating the die or the body so as to provide a continuous Y-shaped slit from one surface to the other surface of the body but wherein the entrance and exit points are transposed rotationally from one another. In the '569 patent, the opposing faces of the disk-shaped body are concave, resembling a dual concave lens having the rotationally translated Y-shaped slit extending therethrough.
In still further attempts to accommodate various diameter therapeutic instruments and varying blood pressure between venous and arterial applications, introducers have employed hemostasis valves of the Tuohy-Borst type. For example, U.S. Pat. Nos. 4,726,374 and 4,723,550 provide at least one hemostasis valve assembled within a housing proximal to the side port, where the housing may be tightened down on the resilient gasket material of the valve to compress it to provide variable pressure seal to the interventional device passing therethrough.
In yet still another approach to providing a suitable seal under the varying conditions of usage encountered in practice, it has also been proposed in U.S. Pat. No. 4,917,668 to spring-load the resilient gasket valve member with one or more spring elements to augment the natural resilience of the gasket material.
The hemostasis valves described above all represent departures from and attempts to overcome deficiencies in flat-sided disk-shaped gaskets involving reduced diameter holes, slits and crossed slits therethrough to accommodate instruments passed through the valve housing and sheath, constituting an introducer sheath. It remains desirable to provide a simple, easy to manufacture hemostasis valve that is reliable in preventing leakage of blood or air and which possesses a feel of smoothness during insertion and withdrawal of all of the aforementioned varying diameter and material instruments therethrough.
The physician is interested in the ability of the valve to seal while not impeding advancement or rotation of the interventional device. The physician desires to be able to feel the movement of the distal end of the interventional device through manipulation of the proximal end or portion thereof. Frictional drag or compression of the interventional device impedes the ability to feel the distal movement thereof.